Colors of M

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Colors of M Ms and Skittles

• Dr. Frank Walmsley
• Trinity University
• San Antonio, TX 78212

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The Rainbow
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The Rainbow As Seen by a Scientist
When the eye sees all the colors of the visible
spectrum, it sees white light.
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The Colors of MMs and SkittlesThe Dyes Used in
Manufacture

• Red Red
• Blue Blue
• Yellow Yellow
• Green
• Brown

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Why are Red MMs Red?

• A red object or a red solution is red because the
  eye sees the red light portion of the visible
  spectrum.
  
• The other portions of the spectrum are absorbed
  by the object or solution and do not reach the
  eye.
  

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A solution in a cuvette

• The colored solution is to be measured.
• The colorless solution is a reference.
• Light of varying wavelength pass through each
  solution and the difference is recorded.
  

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A Red Solution

• Some red color is dissolved from the coating of
  red MMs.
  

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The Spectrometer

• The visible spectrum from 400 nm to 700 nm is
  recorded by a spectrometer.
  
• The spectrum shown on the screen is not the red
  solution.
  

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The Spectrum

• The spectrum of the red solution measured from
  400 nm to 700 nm. Notice no light is absorbed
  from about 600 nm to 700 nm. This is red light.
  

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This light not absorbed
This light absorbed
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Why are Blue MMs Blue?

• A blue object or a blue solution is blue because
  the eye sees the blue light portion of the
  visible spectrum.
  
• The other portions of the spectrum are absorbed
  by the object or solution and do not reach the
  eye.
  

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Preparation of a Blue Solution

• Two MMs placed into water after about 5 seconds.
  Some of the dye is already dissolving.
  

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A Blue Solution

• A solution prepared by dissolving some coating
  from blue MMs as shown in previous slide.
  

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Spectrum of Blue Solution

• The spectrum of the blue solution from 400 nm to
  700 nm. Notice that little light is absorbed
  between about 420 and 470 nm this is blue light.

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This light not absorbed
This light is absorbed
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How Do You Get Green MMswithout Green Dye?

• Can you combine colors?
• Which ones?
• Right!
• Yellow and Blue make Green

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Preparing a Green Solution

• Dissolving the coating from a yellow and a blue
  MM. Notice the green solution forming.
  

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A More Fundamental Question

• WHY do yellow and blue make green?

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Blue Dye
This part not absorbed
Yellow Dye
This part absorbed
This part absorbed
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• Yellow and blue make green
• Because the yellow and blue dyes
• absorb all the colors of light except green.

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• Brown is not a primary color.
• It is a specific combination of other colors in
  specific quantities.
  

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Preparing a Brown Solution

• The coating from brown MMs is dissolved in
  water.
  

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A Brown Solution

• The solution from brown MMs appears sort of
  orange because of its low concentration.
  

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A Black Solution

• How would you make a black solution?
• What would the visible spectrum look like?

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Preparation of a Yellow Solution
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A Yellow Solution
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Spectrum of Yellow Solution
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A Purple Solution

• Prepared by mixing red and blue solutions.

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Spectrum of a Purple Solution

• Notice that there is little absorbance near 400
  to 430 nm compared to large absorbances of the
  red and blue dyes. Notice the wavelength scale is
  not the same as the other spectra.

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Structure of Red 40
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Structure of Yellow 5
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Structure of Yellow 6
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Structure of Blue 1
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Structure of Blue 2